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In a rush to drill based on chasing anomalies, explorers may overlook the structural geology and miss the best drill spots.
by Graham Chandler on June 4, 2012 applied
When geophysicist Hernan Ugalde was contracted by a junior mining company to help define drilling targets, he thought himself fortunate the company had an exploration vice president who believed there was more to it than choosing purple anomalies on remote sensing maps.
“It was an iron exploration project in [Canada’s] Northwest Territories,” recalls the Senior Consulting Geophysicist at Toronto-based Paterson, Grant & Watson Limited. The mining company had flown the magnetics, planning to use map anomalies for direct detection of iron deposits. Since iron is magnetic then the large anomalies should be important targets, went the reasoning. Ugalde and the VP Exploration examined the magnetic data, but to improve confidence, recommended ground field work follow-up. It was fortunate they did. “The field work recognized that the Fe-formation was hematite, which is non-magnetic,” says Ugalde. “Instead of throwing out the data and claiming that the survey didn’t work, we used a think-out-of-the-box approach and modeled 2D sections.” He says working with a structural geologist helped him to separate what was geologically reasonable from what wasn’t. “We ended up with very detailed models that provided the company with targets, on which they will be following up this year.”
The episode points up a valuable lesson for mining companies intent on launching a drilling program in short order after looking at remote sensing data alone; which often happens when eager investors want to see some action.
Ugalde suggests starting from the regional, then going into more detail. He stresses the importance of field work, mapping and measurement of rock properties by the geologist and geophysicist, who should work in tandem. He says in the NWT example "without that, we wouldn't have been able to recognize the different geological units that were the base of the model, instead of the usual blocks with no geological interpretation."
Key is to take time for the geology. “The main challenge is to get the message beyond the ‘can you find me a target?’ stage,” says Ugalde. “It is quite common to see a mining company operating with only one geologist, who is either too busy dealing with all the admin and raising funds, or doesn’t have the background to know what to expect from geophysics.”
Some numbers help drive home his point. “Airborne geophysics with 50 metre line spacing typically provides a resolution of just 10 metres per pixel making definition of precise drilling targets difficult,” he says. “However, once you can make the company understand the value behind the data beyond the drilling frenzy (i.e. extensive structural and lithogical delineation on areas where access is difficult and/or have not been mapped completely), they realize that there is great value in doing this kind of remote sensing mapping.”
The big picture is often overseen. “When companies jump stages on the large-to-small-scale approach, they sometimes lose track of what factors they did use to filter in/out some areas and often end up making an inefficient use of resources,” says Ugalde. “There is a big rush to produce an NI 43-101 [national instrument for the Standards of Disclosure for Mineral Projects within Canada] with proven/inferred reserves.” It requires sampling—drilling—at 50 m, and in the rush to comply, Ugalde says it’s not uncommon that structure is overseen and therefore boreholes are placed where there shouldn’t be any, or at an inefficient attitude/geometry. “To give you an idea, I have seen projects with <100 km of drilling where the general structure was totally overseen, but once you plotted the grades it was quite evident that there was a structural control (folding).” Taking some extra time to analyze the structure would have definitely improved the efficiency of that large drilling program.
In the specific case of geophysics, results can be misleading unless the whole story behind them is addressed. For example, “if borehole planning is based on the wrong information (e.g. K-anomalies associated to lithology instead of alteration; not addressing magnetic inclination and/or remanence; overseeing that in an alteration zone you are interested in the magnetic low around the large purple “blob”), then you’re missing the whole story and this can lead to the waste of those boreholes,” says Ugalde. “It’s easy to just say geophysics did not work, rather than understanding the overall fit.”
Chris Vose, CEO of Brisbane-based Murrumbo Limited, has seen it directly from the explorer side. “In my experience of small cap explorers, there is way too much drilling before there is any understanding of geoscience,” he says. “Shareholders buy on rumor and sell on fact and there is a perception that ‘drilling equals rumor’ and the day traders and punters pump the stock when drilling is underway and results are pending.” He considers the rush to drill is driven by a financial imperative: explorers often lack the ability to communicate their exploration strategy without delivering some headline results for shareholders and investors.
Vose says that as a CEO and engineer he relies upon geoscientific information and advice and often finds geologists differ on their interpretations. “I think that what good geologists do well is to gather evidence before advancing a theory or a model,” he says. “In particular geophysics, geochemistry, structural geology and geochronology are critical to finding mineralisation.”
Though not a junior investment situation, Ugalde uses another example of the value of ground control when interpreting geophysical data: the Bathurst Mining Camp. A producing mine from the 1950s, it was pretty much closed and the Geological Survey of Canada (GSC) funded a new survey; new geophysics. He describes the entire area as 60 x 60 km with very few outcrops. “So we had lots of geophysics but little matching ground control,” he recalls.
“We did some modeling of gravity and magnetic data, in 2D sections. The key here was having me working together with Cees van Staal, GSC’s structural geologist who knew the way the faults were dipping, and how many folded sequences did we need to put on.” Combining van Staal’s knowledge of the area with the resolving power of geophysics, they ended up not only with a great 3D model based on geophysics, but one that made geological sense too.
“The geological input from Cees was invaluable,” says Ugalde. “Modeling is a non-unique problem, so you can put an infinite number of geometries and still fit the data. Having someone who knew what was feasible and what wasn’t was very important.”
Software plays a big role but needs to be applied properly, cautions Ugalde. “We have software that makes life way easier and that almost anyone can operate,” he says. “However, knowing how to use the software is not a replacement for knowing what you are doing from the geoscience perspective.” While a powerful aid, he sees a trend where available software is not being used to its full potential, mostly because of a lack of control on what is actually being done or what is the overall goal. “More access to sophisticated tools needs to be balanced with proper training and field experience.”
To help provide this balance it’s equally important from the software development perspective to ground advanced geocomputing with the right geoscience. Software developer and former exploration geophysicist, Ian MacLeod, Chief Technologist at Geosoft, explains the approach. “We rely strongly on the expertise of our senior scientists, working with industry collaborators, to build and develop new technologies. Impactful technology (based on our experience and understanding of what is proven and effective for exploration) is more important than pushing out the latest feature set.”
“Good technology accelerates labor intensive routines,” says MacLeod, “and it aids in the integration and visualization of the many dimensions of exploration - geology, geochemistry, geophysics, remote-sensing, field mapping, drilling - to help an explorer iterate and best understand their target environment. But proper understanding of all that data, and correct application of the tools, requires sound geological thinking and practical experience.”
What can be done to remedy the lack of interest in ground structural mapping as a geophysics follow-up? Lots of training and going back to basics, figures Ugalde. “We need geologists to understand more about geophysics so that in the future they know what to ask for and what are the limitations of each methodology based on geology, survey specifications etc,” he says. And conversely, “we need to train geophysicists to understand more about geology and see how geological processes affect rock properties and therefore the observed signature.” There’s a need for geologists to go back to basics too. “How many companies are there that actually do structural mapping as part of their standard exploration?” questions Ugalde. “How many companies take the time to build a geological model, rather than just grid the reserves?”
It’s not just software training he reckons, but knowing what to do with the data. “For that, we need to train people at all levels: university level (before graduation), and the current professionals doing the operations.”
Training at the university level is not a simple one he says. Ugalde has completed a PhD so has some firsthand observations. “Universities now have a mandate for self-sufficiency which has led them to teach programs that are more attractive for undergrad students, who are the ones who bring more money (tuition) into the departments,” he says. The result is that more and more geology departments are walking away from hard-rock geology and switching to environmental-based programs because that is what sells to students. “However, nobody bothers explaining to students what kind of jobs they can get with that background,” he says. “For example, talk to a second year undergraduate about a career in mining, he/she will probably refuse because of the bad reputation of non-environmentally-friendly mining.”
Indeed, judging from some recent group discussion on LinkedIn, many geologists are seeing this: a declining trend in hard-rock geology in universities. The trendy shifts today are increasingly on environmental studies, carbon debates, sustainable energy—which need to be explored too—but it is seen as significantly affecting the exploration industry. Structural mapping seems to be on the decline; some consultants are encountering exploration companies which even consider it a waste of time and money. But basic structural mapping by experienced people using the newest technologies should still be seen as a highly cost-effective exploration method.
University co-op programs can work well says Ugalde. Under these, students combine regular university terms with time working in the industry; it exposes them to real problems using real tools. But also “we definitely need to motivate more cross-training (geophysics for geologists; geology for geophysicists) in the industry,” he adds, “so that we develop a common language and everyone is clear on what to get from the data, and what kind of data to use on each situation.”
It may take a while to evolve, but ultimately exploration companies and their investors will realize the value of good structural mapping as an adjunct to their purple blobs.